The proposed program of research investigates the process by which children identify words in speech and associate words to referents. More specifically, it concerns the extent to which very young children may be sensitive to cues in the speech signal which (a) indicate words and other linguistic units and (b) provide information concerning associations between words and referents. This research will contribute significantly to an understanding of how children succeed at the fundamental tasks of identifying linguistically-relevant units in the stream of speech and mapping those units to appropriate real-world referents. The potential role of cues to linguistic units and their referents as initial wedges into language learning will be investigated in four interrelated series of experiments: 1. Infants' sensitivity to cues to word-level units in speech. Tendencies of young infants to perceive certain syllables as especially salient and to treat as a single sequences indicated by particular acoustically based cues will be evaluated using a modified head turn preference procedure, in which preferences for more salient versus less salient changes can be assessed by recording infants' orientation to speakers from which each type of stimulus is presented. 2. Infants' sensitivity to cues to metrical structure. Metrical (rhythmic) structure may' provide cues not only to words, but also to larger linguistic units in speech. The possibility that infants may become tuned to rhythmic properties of their native language will be assessed in experiments using the headturn preference procedure to identify infants' responses to native and nonnative rhythmic patterns across the first year of life. Preferences of Spanish-hearing and Chinese-hearing infants will also be assessed. 3. Interactions between perceptual, representational and production factors. imitation and word-learning studies will be used with two- and three-year olds to disentangle the effects of representational and production factors in contributing to the form of early words. 4. Infants' sensitivity to cues that assist with the mapping of words to referents. Infants' sensitivity to information in the linguistic input concerning the semantic or grammatical categories of novel words will be investigated using a familiarization procedure. Infants will see events involving moving objects. The events will be paired with labeling sequences. If linguistics cues direct 9-16 months-old infants attention toward certain potential referents, then infants should be more likely to notice changes in those particular elements than in other elements of the event. The proposed research may provide insights into the process by which young children identify structure in their native language. By enhancing our understanding of normal language development, valuable information may be provided for early identification and remediation in cases of delayed language acquisition.